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| author | Michal Koutný <mkoutny@suse.com> | 2019-05-31 22:30:19 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-06-01 15:51:31 -0700 |
| commit | bc81426f5beef7da863d3365bc9d45e820448745 (patch) | |
| tree | c26cfabbc7b48e47b65ea33060067dd7b00567c1 /mm | |
| parent | 11bbd8b416f8abf40900dc5041152892f873d915 (diff) | |
| download | linux-bc81426f5beef7da863d3365bc9d45e820448745.tar.bz2 | |
prctl_set_mm: downgrade mmap_sem to read lock
The commit a3b609ef9f8b ("proc read mm's {arg,env}_{start,end} with mmap
semaphore taken.") added synchronization of reading argument/environment
boundaries under mmap_sem. Later commit 88aa7cc688d4 ("mm: introduce
arg_lock to protect arg_start|end and env_start|end in mm_struct") avoided
the coarse use of mmap_sem in similar situations. But there still
remained two places that (mis)use mmap_sem.
get_cmdline should also use arg_lock instead of mmap_sem when it reads the
boundaries.
The second place that should use arg_lock is in prctl_set_mm. By
protecting the boundaries fields with the arg_lock, we can downgrade
mmap_sem to reader lock (analogous to what we already do in
prctl_set_mm_map).
[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/20190502125203.24014-3-mkoutny@suse.com
Fixes: 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Co-developed-by: Laurent Dufour <ldufour@linux.ibm.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/util.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/util.c b/mm/util.c index 91682a2090ee..9834c4ab7d8e 100644 --- a/mm/util.c +++ b/mm/util.c @@ -718,12 +718,12 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen) if (!mm->arg_end) goto out_mm; /* Shh! No looking before we're done */ - down_read(&mm->mmap_sem); + spin_lock(&mm->arg_lock); arg_start = mm->arg_start; arg_end = mm->arg_end; env_start = mm->env_start; env_end = mm->env_end; - up_read(&mm->mmap_sem); + spin_unlock(&mm->arg_lock); len = arg_end - arg_start; |